Glycosaminoglycans (GAG) as hyaluronan and proteoglycans (PG) as dermatan sulfate (DSPG) and keratan sulfate (KSPG) play important role in the structure and physiological functions of cornea. Several corneal pathologies are associated with qualitative and quantitative alterations of GAG and/or PG biosynthesis. For these reasons we investigated the effect of procyanidolic oligomers (PCO) on the biosynthesis and excretion of GAG-s in bovine corneal explant cultures. This was accomplished by the determination of their chemical components, hexoses, hexosamines and uronic acids as well as the incorporation of (35)S-sulfate in the presence and without PCO in the culture medium. In presence of 1 mg/ml PCO total hexoses, hexosamines and uronic acids increased at 5 and 24 h of incubation, hexoses less than the two other components. Stimulation of biosynthesis concerned essentially the uronic acid containing GAG-s, DS and hyaluronan. (35)S-sulfate incorporation decreased in presence of PCO, showing a decreased sulfation of GAG-s. The most striking effect was however the strongly increased excretion of neosynthesized GAG-s in the culture medium. This effect could be beneficial in decreasing corneal hydration in inflammatory conditions, together with the previously demonstrated protection of corneal macromolecules against proteolytic degradation.